act as carriers of the rapidly oxidized lead particles which cling to them. Similar experiments were carried out in letterpress printing works. The average temperature was 370° C. in the stereo pots, and in the linotype pots at work 303° C. Scrap lead melting-pots when hottest registered 424° C., but registered as low as 310° C., according to the amount of scrap added, the state of the fire underneath, etc. The best practical working temperature depends largely on the composition of the metal used. That at some factories is the same for stereo drums as for lino pots--viz., 81·6 per cent. lead, 16·3 per cent. antimony, and 2·0 per cent. tin, added to harden the lead. On the other hand, some printers use a higher percentage of antimony in the lino than in the stereo metal. Lead melts at 325° C., and antimony at 630° C., but by adding antimony to lead up to 14 per cent. the melting-point is reduced at an almost uniform rate to 247° C., after which further addition of antimony raises the melting-point. This explains why temperatures as low as 290° C. are practicable for linotype pots. The molten eutectic has a specific gravity of about 10·5, whereas the cubic crystals average 6·5 only; therefore in these pots the latter float on the top, and excess of antimony is to be expected in the skimmings or on the surface. Administration of certain sections of the Factory and Workshop Act, 1901, would be simplified were there a ready means available for determining the extent of contamination of the air--especially of Section 1, requiring the factory to be ventilated so as to render harmless, as far as practicable, all gases, vapours, dust, or other impurities, generated in the course of the manufacturing process, that may be injurious to health; of Section 74, empowering an inspector to require a fan or other means if this will minimize inhalation of injurious fumes or dust; of many regulations having as their principal object removal of dust and fumes; and of Section 75, prohibiting meals in rooms where lead or other poisonous substance is used, so as to give rise to dust or fumes. Unfortunately, owing to the difficulty hitherto of accurate collection, only a very few determinations of the actual amount of lead dust and fume present in the atmosphere breathed have been made. This lends peculiar value to a series of investigations by G. Elmhirst Duckering, which have thrown much light on the amount of lead fume present in the air of a tinning workshop, and the amount of lead dust in the air during certain pottery processes, and the process of sand-papering after painting. Incidentally, also, they help to determine the minimal daily dose of lead which will set up chronic lead poisoning[3]. Aspirating the air at about the level of the worker’s mouth for varying periods of time, he determined the amount of lead in the fume, or in the dust, per 10 cubic metres of air, and from knowledge of the time during which inhalation took place he calculated